The present invention relates generally to water screens and, more particularly, to traveling water screen systems with collection devices for collecting aquatic life and debris trapped by a water screen.
Water drawn into an industrial plant from a lake or river must be filtered to prevent debris from fouling equipment and causing damage and to protect aquatic life in the lake or river from damage. Traveling water screens are used to filter out and remove debris and aquatic life from an influent channel before the debris can enter the plant or fish impinged on the upstream face of the screen die. A typical traveling water screen comprises a motor-driven screen, such as a foraminous conveyor belt, extending laterally across the width of the channel and vertically from the bottom of the channel to a height above the level of the water to ensure that all the water flowing in the channel passes through the screen. The water screen travels a circuitous path around a motor-driven head shaft above the level of the water and a lower idle shaft in a boot section of the water screen at the bottom of the channel. The screen travels upward along the upstream portion of its circuitous path and downward along the downstream portion. A series of lift elements, such as baskets, scoops, or flights, extending outward of the screen at periodic intervals along its length lift debris or fish trapped on the upward-moving upstream portion of the water screen out of the channel for disposal in the case of debris and safe transit in the case of fish.
A variety of different types of traveling water screen systems is known, including “through-flow pattern” (“transverse flow”), “out-to-in flow pattern” (“dual flow”) and “in-to-out flow pattern” (“center flow”) types. In the “through-flow pattern” type, the screen panels are arranged transversely to the direction of flow of the sluice channel and the screen panels that move downwardly are arranged behind the upwardly moving screen panels in the direction of flow. In the “out-to-in flow pattern” and “in-to-out flow pattern” types of construction, the screen panels are arranged in the direction of flow of the sluice channel. In the “out-to-in flow pattern” type of construction, the contaminated water side is the outside of the upwardly and downwardly moving sections and the clean water side is the interior space between the two sections; the opposite is the case for the “in-to-out flow pattern” type of construction.
For fish handling water screen applications, it is current practice to have a dedicated collection trough for fish and a separate collection trough for debris, as shown in U.S. Pat. No. 8,092,674, the contents of which are incorporated herein by reference. The use of separate collection troughs prevents damage to fish by the high pressure spray water used to clean debris from the water screen.
FIG. 1 shows another water screen system of the prior art 10, comprising a water screen 11 driven by a sprocket 14 and having fish buckets 13 for collecting aquatic life. The water screen includes a trough 12 for collecting the aquatic life and debris trapped by the water screen. The trough 12 comprises a single trough for collecting and combining both aquatic life and debris from the water screen, and a deflector 16 suspended in the trough. A high pressure spray nozzle 18 directs high pressure water through the water screen 11 to push debris trapped by the water screen into the trough 12. A lower pressure spray nozzle 19 provides water for aquatic life dumped by the fish buckets. The deflector 16 blocks the high pressure spray from harming fish falling into the trough from the fish buckets 13. Water, fish, debris and other collected items freely flow below the deflector 16 across the width of the trough 12 and are collected together.